Field of the Invention
The present invention relates to an image sensor, and more particularly, to an image sensor and a method for driving the same capable of improving a readout speed in a binning mode.
Description of the Related Art
An image sensor is a device for detecting optical image signals from the outside and converting the optical image signals into electric signals and has been widely used by being installed in various electronic equipments.
The image sensor has light detecting elements, i.e., pixels arranged along row lines and column lines in a matrix form, and each pixel includes a photodiode for converting incident lights into electrical signals.
A pixel of the image sensor has a small size, and there is a limit to the amount of light which the photodiode can receive. To improve this, the image sensor driven in binning mode has been used.
In a normal mode, an image is formed by using the electric signals generated in each pixel, but in the binning mode, an image is formed by summing electrical signals of neighboring pixels.
According to the conventional art, even in the binning mode, the row lines and the column lines are selected one by one in reading out the signals similarly to the normal mode. Thus, the readout speed in the binning mode is reduced, and the quality of the binned images is degraded because the signal-to-noise ratio is reduced.
Further, it is not easy to increase the frame rate with the conventional art because the signals of the odd-numbered row lines and the even-numbered row lines are read out in the opposite phase to each other so that the time delay is generated between the row lines.